The present invention relates to cutting blades for use in a cutting apparatus of the type employing an elongated canti levered cutting blade and used for cutting layups of sheet material and the like, and deals more particularly with a cutting blade which is of an improved construction having an inexpensive reversible - replaceable edge member insert and an associated insert holder so that the blade remains relatively stiff and is therefore less subject to producing cutting errors arising from lateral or rearward deflection of its lower end.
One type of cutting apparatus used for cutting garment and upholstry fabric and similar sheet materials, as shown for example by U.S. Pat. No. 3,548,697, uses an elongated cutting blade which is part of a cutter moved over the top of a layup of sheet material to cause the cutting blade to follow a desired line of cut, the cutting blade being attached at its upper end to the remainder of the cutter and extending downwardly therefrom in cantilevered fashion through the layup of sheet material and being reciprocated vertically along its longitudinal axis while actively cutting. In such an apparatus, some means, such as a penetrable supporting bed is provided to allow the lower end of the blade to extend downwardly beyond the lower surface of the layup during at least a portion of each of its strokes. Because the cutting blade is cantilevered, forces which are imposed on the lower end portion of the blade by the material being cut, and which are usually laterally or rearwardly directed, tend to deflect the lower end of the blade away from its desired position and, especially when the layup is relatively thick, unacceptable cutting errors may be produced by such deflection with the result that a piece cut from an upper layer of the layup will not exactly match a piece cut from the bottom layer.
One way to reduce the deflection of the blade is to make it from a very stiff material such as tungsten carbide. This has the problem however that tungsten carbide is generally difficult to sharpen and although the edge produced may be suitable for cutting many materials, it may not be of the best character for cutting the material in question because the sharpened edges formed on tungsten blades are generally slightly duller than those produced on blades made of some other materials. The generally preferred material for producing a sharp cutting edge is steel; however, steel has a relatively low modulus of elasticity so that a blade made entirely of steel often deflects an undesireable amount unless it is made of an undesireably large cross-section.
Another way to reduce blade deflection is to use a stiffened cutting blade of the type, as shown for example by my U.S. Pat. No. 3,772,955 and assigned to the same assignee as the present invention, in which an elongated edge member is made of a readily sharpenable material and a strengthening rib is made of a relatively stiff material, the rib being releasably attached to the edge member to stiffen the lower portion of the blade. The blade is assembled and disassembled by flexing the edge member in the proper manner to "snap" the rib into and out of its operative engagement with the edge member. The edge member may be repeatedly sharpened until it is worn beyond a desireable point at which time it must be replaced. A drawback to this type of blade is that the edge member, which is the replaced member of the assembly, is relatively costly. A further drawback is that the assembly and disassembly of the blade may be difficult and awkward since the edge member must be flexed in a specific manner to "snap" the stiffening rib into and out of engagement with the edge member.
The object of the present invention is, therefore, to provide a cutting blade for use in a cutting apparatus of the type employing an elongated cantilevered cutting blade reciprocated along its longitudinal axis and which cutting blade is both stiff to reduce deflection of its unsupported end and uses a low cost, disposable edge member insert having a cutting edge of a desireable sharp character.
A further object of the invention is to provide a cutting blade of the foregoing character which uses an end-for-end reversible edge member insert and a reusable stiffening holder made of a relatively stiff material, the edge member insert being easily releaseable from the holder to allow its reversibility and replacement after the edge has dulled or worn beyond a desireable point.
Other features and advantages of the present invention will become readily apparent from the following written description and the drawings forming a part thereof.